The invention concerns an apparatus for the production of die-cast parts in which the melt is pressured, with the aid of a casting piston under a low pressure, into a die comprising a moving half die and a stationary half die, within the melt solidifies.
The apparatus comprises a casting unit with a drive piston guided in a casting cylinder for the advance of the casting piston. Terminal stops are associated with the casting cylinder for both directions of the movement of the drive piston. The casting piston is aligned with the drive piston and is joined with it. The casting piston is guided in a short casting chamber with a large cross-section held on the stationary die platen, and is capable of being inserted into the movable half die mated with the moving dia platen, and pressing against the runner lug.
A process and apparatus for the production of die-cast parts is known in DE-AS 20 19 502, whereby die-cast parts as free of porosity as possible may be produced with the use of high casting pressure. The disadvantage of casting machines of this type involves the fact that the design of the dies to be employed is restricted by the prevailing high casting pressure and high casting velocities. Primarily, the sand cores used for many castings, for example in gravity die-casting, cannot be employed.
For this reason, a process has been proposed in DE-OS 30 44 992 in which only very low pressures are employed, i.e., lower by one to two orders of magnitude than those employed in pressure die-casting. To obtain the highest possible casting rates, large casting chamber cross-sections and large piston cross-sections are employed.
In the die-casting process for the known die-casting machines, the dies may be adpated to the machine, whereby it is possible, for example, to work with three standard casting members per machine type. However, this is not possible in the new process proposed in DE-OS 30 44 992, which may be designated as a type of pressure mold casting process. If, for example, sand cores are to be used, the filling pressure must be such that the sand cores are not displaced from their position. In order to be able to operate at a low pressure, a high filling degree in the casting chamber is desirable, which requires large casting piston diameters and short casting strokes. The new process further requires that each die have a runner system adapted to tendency of the material to solidify, i.e., the modulus of solidification, with the ingate placed at the region(s) of the die where the solidification modulus of the casting is the highest. These conditions thus render it necessary, in contrast to die-casting machines, to adapt the casting unit to the die. The disadvantage of the pressure mold casting process thus proposed is that always a relatively large effort must be expended on the side of the casting unit, when different castings are to be produced.
It is, therefore, the object of the present invention to provide an apparatus whereby it is possible to use a wide range of casting dies with a single machine, so that the new pressure mold casting process may be applied economically.